The present invention relates to a lens apparatus configured to move a lens in an optical axis direction and an image pickup apparatus such as a digital camera including the lens apparatus.
Mechanisms each moving a lens in an optical axis direction in a lens barrel (lens apparatus) used for a digital camera generally include, as disclosed in, for example, Japanese Patent Laid-Open No. 2008-058581, a cam barrel having a cam groove, and a lens holder holding the lens and having a cam pin that engages with the cam groove.
More specifically, the cam barrel is rotatably disposed inside a straight-movable barrel, and the cam pin of the lens holder engages with the cam groove formed on an inner circumferential surface of the cam barrel and a straight groove formed on the straight-movable barrel. Rotation of the cam barrel moves the cam pin of the lens holder in the optical axis direction by lift of the cam groove with being guided by the straight groove, which moves the lens together with the lens holder in the optical axis direction.
Moreover, Japanese Patent Laid-Open No. 2006-189617 discloses a lens barrel in which steel balls are disposed between barrel members relatively moving in an optical axis direction in order to remove a backlash therebetween in their radial direction.
However, in the lens barrel disclosed in Japanese Patent Laid-Open No. 2008-058581, the inner circumferential surface of the cam barrel and an outer circumferential surface of the straight-movable barrel relatively slide. In this case, a sliding area increases, and thereby sliding noise generated when the lens barrel is driven becomes large.
Further, it is necessary to give a gap between the cam barrel and the straight-movable barrel in the radial direction in order to allow manufacturing errors. The gap deteriorates positional accuracy of the lens. Reduction of the gap for improving the positional accuracy of the lens increases a driving load, thereby resulting in increase in size of an actuator such as a motor rotating the cam barrel.